Generally this invention relates to a system and method of maintaining the integrity of freshly harvested, or freshly cut fruits and vegetables. Specifically, the invention focuses on a distinct series of treatments which confer a lower total microbial count, delay browning, improve general organoleptic properties, and decrease the amount of chemical contaminants on the exposed surfaces without the use of preservatives.
The desire to retain the freshly harvested attributes of produce has been known by the produce, food safety, grocery and canning industries for several decades. Many types of produce, especially that having white flesh, begin to brown shortly after the fruit or vegetable is cut. In mushrooms in particular, the flesh browns as the produce ages, regardless of its having been cut. There are other distinct signs of aging including tissue breakdown (which induces more browning), microbial decay and the like. The desire to maintain freshly picked attributes is important both in the industries where the produce is consumed fresh (within weeks of harvest) and within industries where the produce is to be further processed.
Mushrooms are grown under conditions such that picked mushrooms contain much surface dirt. Moreover, growing conditions and hand-harvesting of mushrooms provides many opportunities for inoculation with spoilage organisms and human pathogens. Mushroom processors are prohibited from mechanically handling and processing mushrooms because of the propensity of mushroom tissue to bruise and subsequently brown. This attribute lowers the commercial appeal and nutritional value of the mushrooms.
Retention of fresh attributes desire has been an acute need within the mushroom industry where rapid browning, and product deterioration severely limits commercial potential and affects production. Browning and product deterioration are biological phenomena governed by enzymatic processes and cellular degradation. The rate of degradation is influenced by several factors including variety, innate levels of browning enzyme, storage temperature, growing conditions, harvesting conditions, bacterial levels, handling protocols and water exposure.
A primary concept for delaying enzymatic browning is the use of chemical compounds to quell effects of the browning enzyme either by inhibiting the enzyme, preventing formation of crucial intermediates, or by excluding or removing substrates of browning enzyme. In the past, many in the produce industry, and mushroom industry, used a solution of chemical preservatives including sodium metabisulfite. Mushrooms were washed with sodium metabisulfite until such treatment was deemed inappropriate for use by the FDA on products to be consumed fresh, as described in a book edited by Lee and Whitaker (1995). A second popular chemical for delaying or slowing browning of produce include treatment with various concentrations of sodium erythorbate and its stereoisomer ascorbic acid Under 21 C.F.R. §§ 170.3 and 182.3041, this ingredient is approved for use on foods by the FDA as a chemical preservative and is GRAS (Generally Recognized As Safe). If a non-detectable amount of chemical remains on the produce after processing then the chemical preservative is reclassified as a processing aid, and does not require inclusion on the ingredients list. The use of sodium erythorbate, alone or in combination with a few other chemicals, was discussed in a U.S. Pat. No. 4,814,192 by Sapers, et al., U.S. Pat. No. 5,919,507 by Beelman, U.S. Pat. No. 4,011,348 by Farrier, et al., U.S. Pat. No. 5,925,395 by Chen, U.S. Pat. No. 5,055,313 by Warren, U.S. Pat. No. 4,818,549 by Steiner, et al., U.S. Pat. No. 6,139,890 by Simpukas, as well as various publications including Sapers, et al. (1990) in a book edited by Wiley (1994), a book edited by Lee and Whitaker (1994) and PMP Fermentation Products, Inc. brochure entitled “Fruit & Vegetables”. Sodium erythorbate functions to control enzymatic browning by acting as a free radical scavenger and chelator, altering the redox potential of the system and/or acting as a reducing agent. There are many other chemicals, or combination of chemicals that can function in a similar capacity as found in 21 C.F.R. §§ 182-184.
In U.S. Pat. No. 5,919,507 by Beelman et al. may employ the concept of chemical compounds, especially sodium erythorbate, on mushrooms in combination with a highly basic solution (as an antimicrobial). Treatment with this combination may be too expensive for commercial implementation and the use of a highly basic solution may be quite dangerous if workers are not sufficiently skilled. If mushroom tissue is not sufficiently neutralized browning can be induced by this treatment due either to cellular damage, or subsequent susceptibility to microbial attack. U.S. Pat. No. 6,287,617 by Bender, et al. may also describe a method utilizing pH shock (a highly basic treatment) followed by a known bactericidal treatment. U.S. Pat. No. 6,262,038 by Pierce et al. may use surfactant and biocompatible fruit acids (acidic pH). These technologies may suffer from the same faults as Beelman et al. coupled with the possible issues surrounding use of non-GRAS, non-process-aid bactericides.
A second method, similar to U.S. Pat. No. 5,919,507 by Beelman is described in U.S. Pat. No. 6,500,476 by Martin, et al. The Martin technology may employ a neutralizing step (acidic pH solution) after treating with basic pH, and prior to sodium erythorbate treatment. This technology requires storage and handling of dangerous chemicals, and may be fraught with disposal and environmental issues associated with acidic and basic solutions including as death of beneficial bacterial in leech field and/or settling ponds. In addition, there is potential for microorganisms on mushrooms to become tolerant to such chemical technology.
Another method which employs sodium erythorbate in combination with hydrogen peroxide as an antimicrobial for treatment on mushrooms is outlined in “Enzymatic Browning Control in Minimally Processed Mushrooms”, Sapers, et al. 1994, Journal of Food Science, V. 59, No. 5, 1994 p. 1042-1047 and “Shelf-Life Extension of Fresh Mushrooms (Agaricus bisporous) By Application of Hydrogen Peroxide and Browning Inhibitors”, Sapers, et al. 2001, J F S: Sesory and Nutritive Qualities of Food, Vol. 66, No. 2, p. 362-366, 2001. This technique may also be expensive in commercial implementation and extremely dangerous for unskilled workers. In addition, hydrogen peroxide at concentrations sufficient to suppress spoilage can induce browning. Hydrogen peroxide is not currently approved by the FDA for use on produce.
An additional method which employs the use of kojic acid is described in “Effect of Kojic Acid on the Oxidation of N-Acetyldopamine by Mushroom Tyrosinase”, Kahn, et al. 1999. Kojic acid is an inhibitor of browning not approved for use by FDA. There are a host of other such chemicals which may inhibit browning but are not approved for use on foods according to sections in 21 CFR.
Another method, described in U.S. Pat. No. 6,224,926 issued to Wrolstad et al. may use antibrowning/antioxidant compounds, specifically an L-cysteine and glutathione derivative, as isolated from pineapple juice, and pineapple processing plants. L-cysteine is commonly used in the produce industry as an antibrowning compound. This treatment alone could not wash mushrooms, or dirty produce.
Another concept for delaying enzymatic browning may be heat inactivation of the browning enzymes. It may not be desirable to heat produce that is to be consumed fresh as heat induces organoleptic changes making it less valuable commercially.
Food safety is an important consideration in all food industries including the produce industry where various spoilage pathogens are detrimental not only to the commercial appeal (organoleptic properties) of the product, but also to the health of the consumer. One example of a pathogen that negatively affects human consumers and is found on mushrooms and other produce is Clostridium botulinum. It is important to reduce the indigenous populations of bacteria and other pathogens to both decrease the risk of illness to the consumer and to increase the useful shelf life of the product.
Mushrooms are subject to visible degradation by various plant pathogens and spoilage organisms. At times, degradation by this cause does not manifest itself until after said mushroom has been harvested and packaged. In addition to affecting the solitary mushroom initially infected, all surrounding mushrooms can be affected and may render the entire package commercially useless. Moreover, excessive moisture on the surface or interstitial spaces of the mushroom can create a micro-environment that increases the susceptibility of the mushroom to microbial or pathogen decomposition.
One concept for reducing the microbial load of produce may be to treat with a highly basic or highly acidic solution. A highly basic treatment is discussed in U.S. Pat. No. 5,919,507 by Beelman and U.S. Pat. No. 6,500,476 by Martin. These treatments do reduce the level of bacteria, and perhaps other pathogens, but may not treat as well as some known antimicrobial treatments that do not work well on mushrooms. Further without proper neutralization, residual acidity can result in damaged tissue that is more susceptible to pathogenic degradation. Moreover, it is possible, and probable that microbes will become resistant to such treatment.
An additional concept for reducing the pathogens on mushrooms may be to treat with ultraviolet light. Ultraviolet light has been utilized for sterilization for over 60 years (see U.S. Pat. No. 2,248,618 by Fisher) and continues to provide a reliable source of surface sterilization. Ultraviolet light causes death to cells and microorganisms via photochemical changes in DNA and cellular proteins, as discussed in the 1998 Jay reference. UV light is commonly used to treat fruitcakes and related products prior to packaging. With limited exposure the ultraviolet light could not penetrate the surface of the produce and could not negatively affect its organoleptic properties, nor induce browning, but it would help to surface sterilize. Ultraviolet radiation may be used in the food industry to create aseptic packaging as described by U.S. Pat. No. 4,121,107 by Bachmann. U.S. Pat. No. 6,171,458 by Rose, et al. may describe use of UV plus ultrasound to sterilize food products, and inorganic products. U.S. Pat. No. 6,165,526 by Newman may describe the use to UV irradiation to decontaminate food in combination with heat and microwaves. This may not appropriate for fresh-cut foods. Ultraviolet radiation use on foodstuffs is also described in U.S. Pat. No. 5,364,645 by Lagunas-Solar, et al.
A further concept for decreasing the microbal load of produce may be to subject produce to ozone. Ozone, triatomic oxygen dissociates into a highly reactive monatomic oxygen. Monatomic oxygen readily oxidizes cellular components. Ozone disinfects through direct oxidation as well as through formation of hydroperoxide intermediates, also bactericidal. Ozone is the fourth most powerful oxidizing agent known with an oxidation potential of 2.07 millivolts (chlorine is 1.35 millivolts) and disinfects approximately 3,000 times faster than chlorine. Ozone delivered in an aqueous solution is 5000 times more toxic than in gas phase.
In addition to disinfections, ozone may be used to deodorize, and remove color. In addition to affecting biota, ozone is also reported to breakdown pesticides, herbicides, and other chemicals as used in the food industry as discussed in U.S. Pat. No. 6,200,618 by Smith et al. There are no known toxic residues or byproducts of ozone therefore disposal may be a mute issue. Moreover, because ozone may be generated on-site and at the time of use, there may be no storage of chemicals, or other potentially dangerous issues.
Ozone is approved as a food additive as found in 21 C.F.R. § 173 and is starting to be used as a technology in the fruit and vegetable industry. Art specific to food may be described in U.S. Pat. No. 6,485,769 by Audy, et al. where utilizing ozone in water may be coupled with mechanical tumbling. This may not appropriate to mushrooms and bruise-prone produce due to the mechanical damage that would be induced. U.S. Pat. No. 6,120,822 by Denvir, et al. may describe the use of an ozone gas in a humid, pressurized environment. Similarly, in PCT Pub. No. WO 90/02572 to Cammiss may describe a technology to disinfect storage rooms and packed produce using ozone gas. U.S. Pat. No. 5,783,242 to Teague may describe a technique for treating food with UV gaseous ozone, or ozone in liquid. Ozone gas alone could not remove the large particulates from the mushroom surface and does not address other organoleptic issues associated with aging mushrooms. U.S. Pat. No. 6,200,616 to Smith et al. and U.S. Pat. No. 5,403,602 to Endico may describe contacting food with an ozone containing wash liquor followed by addition of a surfactant. These technologies may not address physiological browning, nor is the period of immersion (minimum 2 minutes) suitable for mushrooms. Moreover, because this process may occur in one tank, all ozone could be reduced by gross contaminants present in the water after the first batch of mushrooms was washed, and may render ozone treatment ineffective. Similarly, U.S. Pat. No. 5,405,631 to Rosenthal and U.S. Pat. No. 6,132,784 to Brandt et al. utilize UV irradiation and ozone generation (by UV light) to treat fruit. U.S. Pat. No. 6,514,459 to Crisinel, et al. may have introduced a technology to utilize ozone in combination with dirt-removal via tank agitation. Mushrooms generally float however too much agitation can cause them to sink, and could result in water-logged mushrooms. Mushrooms with too much water may lose fresh-cut, organoleptic properties more quickly than unwashed mushrooms.
In addition to delaying browning, and microbial load reduction, there is a desire to rid the mushrooms of growing media for both aesthetic and cleanliness reasons. Mechanical means for reducing macro surface contaminants include, but are not limited to the use of an air knife or similar forced air treatment. As the surface of the mushroom appears to be slightly sticky, this method may not work well.
Mushrooms, and other fruits and vegetables may be treated with various chemicals (herbicides, pesticides, fertilizers, and the like) during growth. The popularity of organic produce underscores the public's perception of residual chemicals on food products. Removal of such could be beneficial to the sale of fruits and vegetables. Ozone may be the only food safe technology which has addressed this issue in an economic manner, as discussed in U.S. Pat. No. 6,200,616 to Smith.
Produce may be washed in either chlorinated water, also a widely used bactericide, or non-chlorinated (organic produce) water flume to remove external contaminants such as dirt. Generally such treatment may not serve to reduce the indigenous population of microbes, rather it may increase said population; however it can remove loose surface impurities. Extended treatment of this type may not be appropriate for mushrooms as excessive water is taken up by the mushroom and causes a surface imperfection called “window paneing”. Window paneing may be commercially detrimental. At chlorine levels sufficient to reduce spoilage organism on mushroom surfaces, browning is induced due to non-enzymatic oxidation of indigenous substrates to form chemicals that serve as browning intermediates. This is noted in the book edited by Lee and Whitaker (1995).
Another concept for sanitizing the surface of fruits, and vegetables as well as other food products may be through the combined used of two or more of the aforementioned technologies. For example, UV and ozone are reported to work synergistically to sanitize exposed surface, and to whiten a product. U.S. Pat. No. 4,156,652 to Wiest may utilize the synergy of ozone and ultraviolet light to sterilize fluids. U.S. Pat. No. 5,213,759 to Castberg may describe the use of UV radiation in an atmosphere of ozone followed by hydrogen peroxide for sterilization of food packaging. Similarly, U.S. Pat. No. 6,162,477 to Crisinel, et al. may describe a process utilizing an aqueous chemical treatment followed by pressurized ozone injection into a tank of aqueous liquid. This process may be designed to be used primarily on fish and therefore may not address cleaning of macro debris, and residual sugars, that will decrease, or nullify the effectiveness of the first solution and/or ozone. This could be overcome by frequent refreshing of the tank; however, this would create inordinate expenses to the processor. The patent may not address removal of excess liquid on the surface of the food product which will affect the quality of the end product. Further, this technology may not exploit the synergy of other antimicrobial technologies with ozone treatment.
U.S. Pat. Pub. No. 20020094363 to Traeder, et al. may describe spraying a food product with ozone plus a surfactant followed by a preserving agent. Because the ozone may be used directly on a dirty, or freshly cut product, the ozone could not oxidize microbial products, but could instead be used to oxidize cellular materials and gross contaminants, thus minimizing, or eliminating its antimicrobial action. Further, a spray system alone likely could be insufficient to remove macro debris, especially on mushroom surface. Sufficient force to remove the dirt could likely result in surface bruising and subsequent browning. Moreover, because this art may suggest collecting, filtering and re-ozonating the wash solution, it is unlikely that ozone levels could be maintained at a sufficiently high levels. Filtration of liquid could not remove all contaminates such as cellular sugars, and organic load could build up in the water, and the ozone could be used to oxidize organic contaminants rather than microbes on the surface of produce.
As in the produce industry and the mushroom industry, the general public clamor for produce that maintains its integrity, its “freshly-picked” organoleptic properties over its shelf life, is treated in a manner safe for workers and consumers alike, and is economically feasible. The present invention discloses a system which overcomes virtually everyone of the aforementioned problems in a practical fashion. It provides a method to rid the produce and mushrooms of growing media, decrease the indigenous level of pathogens, decreases the amount of residual chemical on the surface, and inhibit or slow browning of the surface without inducing negative attributes, nor requiring disclosing of wash ingredients on the finished package.